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Chem Notes
| Question | Answer |
|---|---|
| What is the smallest particle of an element that retains its identity in a chemical reaction? | an atom |
| What instrument can be used to observe individual atoms? | a scanning electron microscope |
| In scanning electron microscopes, a ___ __ _________ is focused on the sample. | beam of electrons |
| Who was the first to propose the existence of atoms? | The Greek Philosopher Democritus |
| Who used experimental methods to transform Democritus's ideas on atoms into a scientific theory? | Jon Dalton |
| Dalton studied the ______ in which elements _______ in chemical reaction. | ratios; combine |
| Dalton observed that when atoms mix, they ______ their own ________ unless they combine in a chemical reaction. | retain; identity |
| Why did Democritus's idea need to be built upon? | It did not explain chemical behavior and was not a scientific theory because it lacked experimental support. |
| What are the three kinds of subatomic particles? | protons, neutrons, electrons |
| Who discovered the electron? | the English physician J. J. Thompson |
| Thompson performed experiments that involved passing ________ _______ through _____ at a low pressure. He used a _______ ___ for these experiments. | electric current; gases; cathode ray |
| Who carried out experiments to find the quantity of an electron's charge? | Robert A. Millikan |
| What is the mass of an electron equivalent to? | 1/1840 the mass of a hydrogen atom |
| Atoms are electrically _______; they have __ electric charge. | neutral; no |
| Electric charges are carried by _________ of ______. | particles; matter |
| Electric charges always exist in _____-______ multiples of a single basic unit; there are no ________ __ ______ | whole-number; fractions of charge |
| When a given number of __________ charged particles combines with an _____ number of positively charged particles | negatively; equal |
| Who observed the cathode ray | |
| Who confirmed the existence of neutrons? | James Chadwick |
| Who discovered that atoms are mostly empty space and discovered the nucleus? | Ernest Rutherford |
| Rutherford's theory needed to be _______. | tweaked |
| What defines an element? | the number of protons in each atom |
| What is the difference between isotopes of the same element? | the number of neutrons |
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alov9636
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